Conventional arrangements of such drive units provide that the speed-transforming transmission is connected at the front end of the electric motor to a portion of the power take-off shaft of the electric motor projecting from a housing of the electric motor. This results in a relatively large overall size for the drive unit, especially in the direction along the rotational axis of the electric motor (overall length), which is disadvantageous for many applications.
Starting from this prior art, the invention was based upon the object of specifying a drive unit with an electric motor and a speed-transforming transmission, which is characterized by the most compact possible overall size and especially overall length.
This object is achieved according to the invention by a drive unit according to claim 1. A combination of such a drive unit with a unit to be driven forms the subject matter of claim 7. Advantageous embodiments of the drive unit according to the invention and of the combination according to the invention of drive unit and unit to be driven form subject matters of the other claims and are derived from the following description of the invention.
In the case of a drive unit with an electric motor and a speed-transforming transmission connected in a rotationally driven manner to a power take-off shaft of the electric motor, in which the electric motor comprises a stator and a rotor comprising the power take-off shaft, it is provided according to the invention that the speed-transforming transmission is arranged (at least partially) inside the power take-off shaft constituted (in at least one portion) as a hollow shaft. In this context, the rotor can be arranged both (at least partially) inside (so-called internal rotor) and also outside (so-called external rotor) the stator. Through the at least partial arrangement of the speed-transforming transmission inside the electric motor, which is allowed by the embodiment of the power take-off shaft as a hollow shaft, a compact overall size and especially overall length for the drive unit according to the invention can be realized.
Alongside such a drive unit, a combination according to the invention comprises at least one unit to be driven, which comprises a static part and a rotatable part, wherein the rotatable part is provided for a rotationally driven connection with an output component, especially an output shaft, of the speed-transforming transmission.
By preference, it can be provided that the speed-transforming transmission is constituted in the form of a transmission unit which, alongside the transmission components (for example, wheels) guaranteeing the speed-transformation, also comprises at least one transmission housing (which can itself represent one of the transmission components) surrounding individual components or all of the transmission components. By particular preference, it can be further provided, here, that the transmission unit is embodied in an encapsulated manner, so that the latter completely surrounds all transmission components and comprises as far as possible only (preferably sealable) passage openings for an input shaft and an output shaft or for components (especially the power take-off shaft of the electric motor and a drive shaft of the rotatable part of the unit to be driven) provided for the rotationally rigid connection to the input shaft and the output shaft. Optionally, further, preferably sealable, maintenance openings can be provided, for example, for the lubrication of the transmission components with a lubricant.
In one preferred embodiment of the drive unit according to the invention and therefore also of the combination according to the invention, it can be provided that the electric motor is constituted as a servomotor. The electric motor is accordingly constituted in such a manner that, through the integration of at least one sensor and the evaluability of the measured values of this sensor in an evaluation unit, it allows a control at least of the angular position of the power take-off shaft and, derived from this, preferably also of the rotational speed and/or the angular acceleration. In this context, by further preference, a control for the angular position and/or one or more parameters derived from the angular position can be provided.
By further preference, it can be provided that the speed-transforming transmission is constituted as a planetary gear or at least comprises a planetary gear. In particular, planetary gears can comprise the advantage of a compact overall form at the same time as large speed-transforming ratios.
A combination according to the invention of the unit to be driven and such a drive unit with planetary gear can be advantageously further developed in that at least one transmission component of the planetary gear is connected in a rotationally rigid manner to the static part of the unit to be driven. In this manner, the possibility of the planetary gear being rotated together with the power take-off shaft of the electric motor can be avoided.
In one preferred embodiment of the drive unit according to the invention, a drive housing (at least partially) accommodating the electric motor and the speed transforming transmission can be further provided. In particular, this can be provided for the rotationally rigid attachment of the stator of the electric motor and/or for the attachment of the entire drive unit to its attachment structure, for example, to the static part of the unit to be driven. In one preferred embodiment of the combination according to the invention, it can therefore be provided that the drive housing of the drive unit is connected in a rotationally rigid manner to the static part of the unit to be driven. Additionally or alternatively, it can also be provided that the stator of the electric motor is connected in a rotationally rigid manner to the static part of the unit to be driven.
By further preference, it can be provided with such a drive unit that the power take-off shaft extends beyond the stator with a bearing portion, at least at one longitudinal-axial end, and is mounted in a rotatable manner in this bearing portion, inside the drive housing, thereby achieving a design advantage in the bearing for the rotor of the electric motor.
The indefinite articles (“a” and “an”) should be understood as such and not as numerals, especially in the claims and in the description explaining the claims in general. Correspondingly specified components should therefore be understood in the sense that these are present at least once and can be present multiple times.